In order the play the map you have to extract the files with winrar (or another program). This will yield a map file and sometimes a read me, screen shots, and other unnecessary files.
Once you have the map file, go into my computer (assuming you have windows), find the halo ce file. Inside this file there should me a folder with maps in it (bloodgulch, dangercanyon, the original maps). Just simply place the map in this folder.
I really hope this helps, if i can help in any other way please let me know.
ps. sorry if i just walked u through something you already did.
